Argon Gas Supply Calibration in Metal Powder Atomization
Precision calibration of argon mass flow and trace purity controls particle size distribution and prevents interstitial oxide formation in atomized powders.
Cavity Ring down Spectroscopy
Meaning
Optical absorption measurement using the rate of decay of light trapped in a highly reflective resonant cavity provides sub parts per billion sensitivity for trace gas analysis. In cavity ring down spectroscopy, a laser pulse is injected into a chamber bounded by two highly reflective mirrors, and the light reflects back and forth thousands of times. The intensity of the leaking light decays exponentially over time, with the decay rate depends on the absorption of the molecules inside.
Optical Decay
Quantitative calculations rely on the difference in the decay time between an empty cavity and a cavity containing the sample gas. A typical empty cavity decay time might be several tens of microseconds. When absorbing molecules are present, they shorten this ring down time.
Highly reflective mirrors, often exceeding ninety nine point nine nine percent reflectivity, are required to sustain the long optical path length.
Trace Detection
Impurity monitoring in ultra high purity industrial gases utilizes this method to detect moisture and hydrocarbons. This rapid response time allows the instrumentation to detect process excursions almost immediately.
Laser Alignment
High precision mechanical mounts hold the optical elements to prevent thermal drift from disrupting the resonance. A piezo electric transducer adjusts the cavity length to match the laser wavelength. This fine tuning keeps the system in resonance to ensure reproducible decay curves.